This invention relates to the production of halomethylated polystyrene also denominated poly(halomethylstyrene). More particularly, it relates to a new method for forming this material by halomethylating polystyrene.
Chloromethylated polystyrene and, to a somewhat lesser extent, bromomethylated polystyrene are established commercial materials. These materials probably find their largest use as precursors to ion exchange resins. They also are now finding increasing utility as substrates for the attachment of active groups to yield polymeric reagents.
Conventionally, the halomethylstyrenes have been formed by reacting polystyrene with a halomethyl methyl ether, especially chloromethyl-methyl ether, Cl--CH.sub.2 --O--CH.sub.3, in the presence of aluminum trichloride or an equivalent Friedel-Crafts alkylation catalyst. Recent findings have made this method unattractive, however. Chloromethyl-methyl ether has been placed on the Federal Government's OSHA (Occupational Safety and Health Act) list of compounds whose use is restricted because of potential carcinogenicity. Additionally, commercially available chloro-methyl-methyl ether or the bromo equivalent generally contains a small amount (1-3%) of di-halomethyl ethers, (Br--CH.sub.2 --O--CH.sub.2 --Br or Cl--CH.sub.2 --O--CH.sub.2 --Cl) which materials are known to be highly carcinogenic.
This problem has required the use of new ultra-safe facilities to produce the chloromethylated polystyrene product. The cost of such facilities is prohibitively high and has forced up the price of the finished chloromethylated polystyrene product among large producers or has driven smaller producers out of the business.
A new method for preparing halomethylated polystyrene which did not require halomethyl-methyl ether thus would be of advantage.